1. Field of the Invention
The present invention relates to a perpendicular magnetic recording medium and a method for manufacturing the same. The present invention relates to a perpendicular magnetic recording medium preferably mounted on various magnetic recording devices such external recording devices for a computer, and to a method for manufacturing the perpendicular magnetic recording medium.
2. Description of the Related Art
A recording method for a magnetic recording medium used in a magnetic recording device, such as a hard disk, a magneto optical drive (MO) disk, or a magnetic tape, includes two types of longitudinal magnetic recording and perpendicular magnetic recording. As a recording method used for the hard disk, the longitudinal magnetic recording has been employed for many years, in which magnetic patterns horizontal to the disk surface are recorded. However, an increase in recording density has made noticeable a problem of thermal fluctuations, that is, a problem of disappearing recorded magnetization due to thermal energy. Additionally, with the increase in recording density, the longitudinal magnetic recording also has caused a problem of having unstability in a site where the same poles of magnetizations face each other. Thus, since around the year 2005, the perpendicular magnetic recording enabling a higher recording density has been used in which magnetic patterns perpendicular to the disk surface are recorded. Recently, almost all magnetic recording media used are perpendicular magnetic recording media.
Heretofore, studies on metallic magnetic materials for perpendicular magnetic recording media have been concentrated on magnetic layers made of CoCr-based non-ordered alloys including CoCrPt. Nevertheless, in consideration of anticipation of perpendicular magnetic recording media also having a thermal fluctuation problem in the future as fineness of recorded magnetic patterns increases, the material needs to have a larger perpendicular magnetic anisotropy than conventional CoCr-based materials. As a leading candidate, ordered alloy-based materials have been actively studied. Such ordered alloy-based materials have an ordered phase formed of, for example, at least one magnetic element selected from Fe, Co, and Ni, and at least one noble metal element selected from Pt, Pd, Au, and Ir. Particularly, FePt and CoPt, ordered alloys having a fct crystal structure, are known to have a magnetic anisotropy as large as 7×107 erg/cm3 and 4×107 erg/cm3, respectively, in a c-axis direction that is an easy axis of magnetization. The magnetic anisotropy of these is twice or, more of values obtained by CoCr-based materials currently. Patent Literatures 1 to 6 noted below describe L10 type ordered alloys such as the FePt and CoPt ordered alloys and a FePd ordered alloy, as well as magnetic recording media using such alloys as a magnetic layer.
Researches are in progress to apply a polycrystalline thin film having a large magnetic anisotropy in a c-axis (easy axis of magnetization) direction as described above to a longitudinal or perpendicular magnetic recording medium.